全新java初学者实践教程6(Java SE5.0版)
$q$7^r@ 基本语法3
JH8}Ru%Z eJ0?=u!x &V7M}@ 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
pO7Zs n]}W``=7 [font="Times] 1.循环语句[font="Times]:while,do-while,for
l12{fpm r V6/Tdy [font="Times]2.分支语句[font="Times]:if-else,switch,
gw36Ec<M [font="Times]
oGa^/:6L 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
Hc^W%t~ [font="Times]
tM4Cx 4.异常处理语句[font="Times]:try-catch-finally,throw
TX=yPq T4)fOu3] 实践:
m3bCZ9iE [font="Times] 1.循环语句
) ZfdQ3 [font="Times] while 语句
D^Jk@<* [font="Times]class While {
/FD5G7ES [font="Times]public static void main(String args[]) {
?W>qUrZ [font="Times]int n = 10;
qpIC{'A. [font="Times]while(n > 0) {
ntFT>g{B [font="Times]System.out.println("tick " + n);
!|ak^GE:(% [font="Times]n--;
3 ZEB [font="Times]}
T*g:#
^4 [font="Times]}
i|`dWOVb [font="Times]}
]:>,A@7 [font="Times] do…while 语句
i4JqT \q [font="Times] class DoWhile {
Fz#X=gmG [font="Times]public static void main(String args[]) {
bKg8rK u [font="Times]int n = 10;
2i;7{7 [font="Times]do {
:cB=SYcC% [font="Times]System.out.println("tick " + n);
oVFnlA [font="Times]n--;
;oZ)Wt [font="Times]} while(n > 0);
R;,g1m|] [font="Times]}
&>d:R_Q] [font="Times]}
>NYW{(j 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
wX >*H [font="Times] for语句
#$1Z [font="Times] class ForTick {
k:jSbbQ [font="Times]public static void main(String args[]) {
I[)% , jd [font="Times]int n;
mKrh[nA [font="Times]for(n=10; n>0; n--)
h2ytS^ [font="Times]System.out.println("tick " + n);
7frTTSZ [font="Times]}
%\]*OZ7 [font="Times]}
L:XC 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
X+UJzR90 还有啊,[font="Times]for循环的部分可以为空的
*na?n2Yzt [font="Times]class ForVar {
A,sr[Pa@ [font="Times]public static void main(String args[]) {
V |(H|9 [font="Times]int i;
YIw1 [font="Times]boolean done = false;
~ab:/!Z [font="Times]i = 0;
T,aW8| [font="Times]for( ; !done; ) {
vz.>~HBP [font="Times]System.out.println("i is " + i);
Po%LE]v, [font="Times]if(i == 10) done = true;
[sB 9gY( [font="Times]i++;
F*"}aP$ [font="Times]}
&f-Uyr7? [font="Times]}
S<'[%ihx [font="Times]}
循环语句的例子下载 F~h7{@\ [font="Times] 2.分支语句[font="Times]
.o) `m9/ [font="Times] if/else语句
C74a(Bk}H [font="Times]class IfElse {
/c
uLc^(X [font="Times]public static void main(String args[]) {
i3rH'B-I. [font="Times]int month = 4; // April
eek7=Z [font="Times]String season;
|{CfWSB7~@ [font="Times]if(month == 12 || month == 1 || month == 2)
8Z(Mvq]f& [font="Times]season = "Winter";
:q#Xq;Wp [font="Times]else if(month == 3 || month == 4 || month == 5)
:Nofp& [font="Times]season = "Spring";
phM>.y_ [font="Times]else if(month == 6 || month == 7 || month == 8)
|*}4 m'c [font="Times]season = "Summer";
15o9 . [font="Times]else if(month == 9 || month == 10 || month == 11)
0PlO(",a [font="Times]season = "Autumn";
w!fE;H8w6 [font="Times]else
|PC*=ykT3 [font="Times]season = "Bogus Month";
j~!X;PV3 [font="Times]System.out.println("April is in the " + season + ".");
~l)-wNqR4r [font="Times]}
J0@X<Lt U [font="Times]}
Q~Hy%M%R3 [font="Times]//这段程序输出[font="Times]:
tQS5hwm* [font="Times]//April is in the Spring.
: |>Gc39`t [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
+E{|63~q [font="Times] switch语句
s&RVJX>Rt [font="Times] class Switch {
6Vz9?puD [font="Times]public static void main(String args[]) {
\[y`'OD~ [font="Times]int month = 4;
PYGRsrcFd# [font="Times]String season;
)jt #=9ZQ [font="Times]switch (month) {
A!h`]%0B [font="Times]case 12:
D8$G `~hD [font="Times]case 1:
@nux9MX<9 [font="Times]case 2:
v%q0OX>9X" [font="Times]season = "Winter";
<yd{tD$A* [font="Times]break;
3\XU_Xs(] [font="Times]case 3:
*s:(jDlv [font="Times]case 4:
r-Pkfy( [font="Times]case 5:
H ' [font="Times]season = "Spring";
3f,hw5R [font="Times]break;
/pT=0= [font="Times]case 6:
B]Thn [font="Times]case 7:
*{L)dW+: [font="Times]case 8:
H !$o$}A [font="Times]season = "Summer";
1,% R;7J=g [font="Times]break;
{GQ^fu;q [font="Times]case 9:
INJEsz [font="Times]case 10:
cLLbZ=` [font="Times]case 11:
iv4H#rJ [font="Times]season = "Autumn";
`hQ5VJo [font="Times]break;
Fvbh\m
~ [font="Times]default:
4rLL[?? [font="Times]season = "Bogus Month";
]@phF _ [font="Times]}
sG
F aL [font="Times]System.out.println("April is in the " + season + ".");
]x(!&y:h [font="Times]}
{0WHn.,2Y [font="Times]}
分支语句代码下载 8|\8O@ a6uJYhS~ [font="Times]switch语句适合于条件非常多的逻辑
|>dI/_' 请看上述语句可以混合使用,请看
下载例子